The present invention relates to a liquid crystal display which displays an image through the use of a cold cathode fluorescent lamp (CCFL).
Liquid crystal displays are classified into several types according to lighting methods at the time of displaying an image. A typical liquid crystal display is a translucent liquid crystal display using a light source (a so-called backlight) disposed behind a liquid crystal panel. As such a light source, a cold cathode fluorescent lamp (CCFL) which is generally called a cold cathode tube is used.
For example, as a cold cathode fluorescent lamp for LCD television, Y2O3:Eu, LaPO4:Ce, Tb and BaMgAl10O17:Eu are typically used as a red phosphor, a green phosphor and a blue phosphor, respectively (for example, refer to “Phosphor Handbook” edited by Phosphor Research Society, First Edition, Ohmsha, 1987, p. 219, p. 228, and T. Takahashi, “Color filter for liquid crystal display”, Journal of the Imaging Society of Japan, 2002, Vol. 41, No. 1, p.68). Y2O3, LaPO4 and BaMgAl10O17 are matrix materials, and Eu and (Ce, Tb) are luminescent centers.
FIG. 7 shows emission spectral characteristics of each color phosphor. In the drawing, a red emission spectrum R101, a green emission spectrum G100 and a blue emission spectrum B101 show the emission spectra of the red phosphor Y2O3:Eu, the green phosphor LaPO4:Ce, Tb and the blue phosphor BaMgAl10O17:Eu, respectively. The cold cathode fluorescent lamp as a backlight emits white light by such emission spectral characteristics of each color phosphor. Then, the white light is divided into primary colors, that is, red (R), green (G) and blue (B) by a color filter arranged in each pixel of a liquid crystal panel so as to display a color image.